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<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
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    <div id="root">Hello,学习jQuery</div>
    <script>
        var root = document.getElementById("root");
        root.innerHTML = "修改之后的内容,hello";
    </script>
</body>

</html>